Test stations for radar systems and the like often require means for generating radio frequency (RF) stimuli featuring frequency modulation (FM), phase modulation (PHM) and amplitude modulation (AM) with ultrafast tuning rates and wide deviations.
Prior art RF signal generators employ the type of oscillator commonly known as a YIG oscillator as the RF signal source. This type of oscillator has a relatively broad RF frequency range and a relatively good signal to noise ratio and high frequency accuracy. The YIG oscillator, however, is not capable of the fast tuning rates needed to provide fast wide deviation frequency modulation as is required for the intended purposes.
Another type of oscillator, commonly known as the varactor oscillator, is capable of the required fast tuning rates but is not particularly suitable for the intended purposes because of its inferior signal to noise ratio, linearity, temperature stability and RF frequency range compared to the aforenoted YIG oscillator.
In view of the above, it will be understood that the required capabilities of equipment for the intended purposes are beyond frequency generators now known in the art. Accordingly, it is the object of this invention to provide an RF signal generator which combines the features of the aforenoted (YIG and varactor) oscillators to generate radio frequency signals for the intended purposes.